During flight, aircraft track is not always the same as aircraft heading. For example, in the presence of crosswinds, an aircraft often has to adjust its heading in order to follow a desired course or track. As a result, some displays are track centered, others near-track centered and others are heading centered. Each type of display has its advantages and disadvantages.
In many flying situations, track centered displays have various advantages over heading centered displays. For example, a heading centered display is particularly sensitive to motion of the craft such as motion due to strong crosswinds. This motion can cause a flight path marker on the display to move around and collide with other flight symbology. This can be very distracting to a flight crew. A track centered display or a near track centered display, however, is substantially centered on the direction of travel. As a result, it is not as sensitive to craft motion and works well during flight.
A track centered or near track centered display, however, is not the best choice of displays during certain circumstances such as landing of the aircraft. When landing, the nose of the aircraft should be aligned with the direction of travel for safety purposes. In other words, the heading and track should be substantially aligned. If a flight crew is relying on a track centered display during a landing approach, everything may appear to be lined up correctly on the display since the track centered display is centered substantially on the direction of travel, but in reality the nose of the craft is not aligned. When the flight crew looks out a window, the scene will be different from the display. In fact, if the heading and track are sufficiently different, the runway may not even be directly visible out the window. This can be very startling and confusing to a flight crew.